Jet ink is typically liquid which tends to follow paper fibers when printed on paper. When printing dots are one three hundredth of an inch (1/300 inch) or larger, such spreading is noticeable when black ink is printed beside typical colors of the visual spectrum. U.S. Pat. No. 5,168,552 to Vaughn et al and European Patent Application 595 650 A2 published May 4, 1994, of Moriyama et al recognizes this disadvantage and attempts to cure it by printing three color black (often termed process black) on the boundary between color and black. This invention employs a pattern of black ink and process black at such borders. European Patent Application 596 373 A2 published May 11, 1994, of Sato et al discloses in its FIG. 12A-FIG. 12D a pattern as employed by this invention, but each pixels is much larger than those of a pattern used to control bleed in accordance with this invention.
U.S. Pat. No. 5,220,342 to Moriyama teaches alternating black ink and process black to speed printing, not with reference to a border of black and color in the image to be printed. U.S. Pat. No. 4,682,216 to Sasaki et al employs alternating process black and black ink when black intensity is to be a certain level. U.S. Pat. No. 5,057,852 to Formica et al employs overlapping dots of process black and black dye to improve and smooth the edges of black images. U.S. Pat. No. 5,012,257 to Lowe et al employs a pattern of printing on diagonals to minimizing bleed across color boundaries.